Marker for blackboards



April 1953 P. E. WHITTINGTON 2,636,275

MARKER FOR BLACKBOARDS Filed Nov. 14, 1949 2 SHEETSSHEET 1 29 I r I:

g. ":39 [F7 g 736 L9 v a April 1953 P. E. WHlTTINGTON 2,636,275

MARKER FOR BLACKBOARDS Filed Nov. 14, 1949 2 SHEETSSHEET 2 BY wax.

' ATTORNEY Patented Apr. 28, 1953 ITED STATES PATENT OFFICE MARKER FOR BLACKBOARDS Paul E. Whittington, Arlington, Va. Application November 14, 1949,,Serial No. 127,212

12 Claims. (01. 33-86) (Granted under Title 35, U. s. Code (1952), see. 266) The invention described herein, if patented, may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to devices for marking blackboards and the like with chalk lines.

In the Allen Patent No. 253,490, dated February 14, 1882, a device is shown for marking cloth, etc., with a plurality of equally or unequally spaced parallel chalk lines. My invention employs an open frame having a number of parallel chalked cords or strings, as in the Allen patent, but is an improvement in the following particulars, among others:

1. The marker frame and cords may be manipulated to provide not only equal spacing of the cords but also logarithmic spacing, and probability spacing, and combinations of these spacings.

2. The marker frame may be disassembled after the cords are removed to facilitate packing in a small space for storage or shipment.

The invention has other advantageous features as will be apparent from the following description of the preferred embodiment thereof and certain modifications, in connection with the accompanying drawings forming a part of this specification.

In said drawings, a

Fig. 1 is a plan view the cords arranged for or scales;

Fig. 2 is a plan view of one corner of the device, on an enlarged scale;

Fig. 3 is a cross section on two logarithmic spacings line 3-3 of Fig. 2

but on a still larger scale;

Fig. 4 is an elevation of one of the corner pieces, on the scale of Fig. 3;

Fig. 5 is a cross section on line 5--5 of Fig. 2, on the scale of Fig. 3;

Fig. 6 is a detail in elevation showing the engagement of one end of a chalking cord with the frame;

Fig. 7 is a plan view of the device of Fig. 1 but shown arranged to make two sets of parallel lines at right angles;

Fig. 8 is detail in cross section of a slight modification;

Fig. 9 is a modification;

Fig. 10 is a detail plan view of still another modification; and

Fig. 11 is a detail in cross section showing how the cord end is held by the form of Fig. 10.

Referring particularly to the drawings, and

of the device shown with detail in cross section of another first to Figs. l-5, the preferred form of blackboard marker consists of a four-sided open frame l5 which is preferably square, being made up of four channel pieces 16, I1, I8, l9 and four like corner pieces 20, all preferably made of stainless steel or other non-corroding metal. Secured to the frame under tension by means to be described are a plurality of chalking strings or cords 2| which when coated with ordinary chalk may be snapped individually by the fingers of the operator against a blackboard or other surface to make lines thereon having the desired spacing. The corner pieces are each angular or L-shaped, with two equal. legs having reduced ends 22, 23 which may be square in cross section, as shown, but in any case will be properly shaped and dimensioned to permit endwise insertion and snug fitting in the ends of the channel members, so that each pair of adjacent channel members are held together at right angles by a single corner piece. Shoulders 24 on each leg limit the inward movement of the corner piece relative to the channel with which it is being assembled. The construction is such that the two outer plane surf-aces of each corner piece 20 are flush with the respective outer surfaces of the two frame members which are held together by each corner piece, as shown in Figs. land 2. As the form of Figs. 1-5 cmploys corner pieces square in cross section fitting square channels, it is also possible to insert the corner members by pushing them laterally into the spaces between the flanges of each channel. However the corner I pieces are inserted, they must fit snugly enough (in the form of Figs. 1-5) to be held securely by friction. Then the four channel members will be held together in the same plane without likelihood of separating when the device is in use. The channel members are rigid but have sufficient spring to permit the slight separation necessary to permit the last corne'r piece to be inserted after three corner pieces are in position.

Instead of the corner pieces being held by friction alone, which requires careful finishing of the abutting surfaces, positive locking means may be employed, for example the bolt 25 and wing nut 26 of Fig. 9. There will be one bolt 25 passed through each reduced end 22, 23 of each corner piece. This form has the advantage of a secure fastening at each of the corners of the frame, but requires the removal and replacement of eight wing nuts each time any changeis made in the relative positions of the frame components. In the form of Fig. 8, the channel flanges have inturned wings 21 which hold the corner pieces more securely but compel insertion of the corner pieces to be by endwise movement only.

With the frame assembled, the chalking strings or cords 21 are secured according to the desired pattern. Each cord 2! has a knot 28 at each end and after being. passed under a channel it isslipped through notches, 30 (to be described): cut in the upper or outer edges of theflanges of the several channels (as will be understood from Figs. 5 and 6) and the knot is located in back of the notch as shown. The knotstareofaconrse spaced apart so as to insure the requisite tension in the cords when secured to the-frame at' both. ends. In the form of Figs. andl-ll,..-the-.cord.-.2l-. is passed through a triangular centering aperture 3i punched in the bottom wall tl2 of-the'. channel and then is brought upv into engagement. with notch 38 on the inner flange of the channel. This form is advantageous in that the cords are centered relative to the notches into which they are moved; also the'converging' walls ofthe of each triangular aperture 31 act togrip the cord by friction and hold it while the cord is slipped into the notch, which isa convenience in assembling cords" stretched taut. It is, however, more difiicult'to threadthe knotted cordsthrough the apertures 3| than merelytopass them around the outside walls of a channel.

Referring to Fig: 1, the notches 28 in the outer flange of channel it? and notches-33' inthe outer flange of the opposite channel it have exactly the samespacing along the channels, this spacing being a double?logarithmicarrangementi When cords 21' are secured. in all the notches" 29, 3'3 as shown, and then" are chalked,- theframe may be held against'a' blackboard and the cordsin-di vidually plucked or snapped to mark the bl'acltboard with a set oflogarithmicco-ordinate's; It will then be easy'fortheuser'to draW'a'logarithmic curve onthe=board without taking ti'meduring a lecturetomake measurements; which would cause loss of attention on th'e'partoftheauditors;

Still referring to Fig. 1, the" inner flangeoi channel 16' andthe'corresp'onding flange'of chan= nel :3 are both provided with' notches 38', 35 spaced in a single logarithmioseries; To" employ these notches the framei's-taken apart and then channels it" and It are reversed end for end to bring the inner flangesof Fig; 1- outermost.- If the construction ofFigs. 10 and 11- is used; however, it is possible to-space the cordsaccord ing to the spacing of the inner notches without disassembling" the device and reassembling it; since a cord" maybe secured as desired" without alteration ofthe frame: This will beund'erstood by examining Fig: II.

The other two channels IT, f9 have notches 36', 3'! respectively cut' equal distances apart, say oneiin'ch, along the outer'flanges. Alsochannels' I l, mhave notches 3'8; 39" respectively along the inner flanges; spaced accordingto themathematica-l theory. of probability; Channel's l7, t9- must be reversed, after disassemblingthe frame, in order to attach the cordstoexten'd in a series arranged in accordance with-thetheory'of probability, unless the constructionof Figs. 10 and 11 is employed. Channels ll, l9 thus permit the user to rnark vertical lineseqnally'spacedapart or alternatively probability" lines; andif desired the frame may be turned 90 to make these=lines horizontal instead of vertical.

In Fig. '7' the" frameis shown with channels Il-I is holding tensione'd horizontal cords 21a spaced equal distances apart (say-2 in.) also with slightly modified channels it; lfl'l turnedoverto brlng the TOT ries of equally spaced horizontal co-ordinates on the:blackboa-rdand then the frame may be turned completely over and held so that the cords in the double: logarithmic series are adjacent the blackboand,,whereupon a series of vertical lines arranged in a double logarithmic series may be marked'on the board in addition to the horizontal cQ-ordinates Alternatively, the horizontal lines may'lie"probability lines (if channels I! and 19 are reversed end for end) and the vertical lines may be in single logarithmic series.

Thedescribe'd constructionwvithproper manipulationpermits the-following chalk markings. on a blackboard:

1. Lines" in a single logarithmic series, extending vertically orhorizont'ally.

2. Lines in double logarithmic; series,v extend ing'vertically (Fig; 1) or horizontally;

3. limes equally spaced" apart and extending vertically or horizontally (Fig. 7')

a. Lines spaced in conformity with the mathematical theory of probability, and extending vertically or horizontally.

5. Single'log: series linesrunning vertically, and single log. series lines running horizontally..

62 Single log. series lines (either horizontalor vertical-r with double logi series (either vertical or horizontal).

71 Douhle log. series lines arranged vertically with double log. lines arranged horizontally.

8. Single-log: series lines- (either horizontal or vertical) with equally spaced lines (either-vertical or horizontal).

9. Double log. series lines- (either hoiizontal or vertical) Witlrequa-lly spaced lines (either vertical-or horizontal). See'Fig'. 7.

I0: Single-log series lines (either horizontal or vertical) with probability" lines (either vertical or horizontal).

11. Double log. series lines: (either: horizontal orvert-ical) with "probability line's (either vertical or horizontal);

12. Equally spaced lines (either horizontal: or vertical) with probability line's: (either. vertical or horizontal).

Equally spaced lines arranged: both horizontal and vertically.

14. Probability lines arranged both. horizontally ant vertically.

It-w-ill be clear that-the frame-may be held at any angle to the horizontal so that'severalseries of lines may be markect on: the board at angles to the vertical or horizontal- Also the invention is not limited to the described line spacing other. spacings oflthe: notches mayfbe resorted to, and other arrangementsiof thenotched channels may be used. While notches have; been described and shown. as the; most: convenient means" for securing the cords, other means, such as small. pins arranged in. pairs, could be. employed to hold the knots on the cord ends. Various other departures from thee-described oonstructioniand operation may be made if within. the scope of the appended claim.

It will beappreciatedlthat as th'eifour corner pieces are readily removable: from the: channel members, the device is easily packed into a small space, which is a convenience for storage or shipment.

What I claim is:

1. A device of the character described comprising a rigid frame having a central opening and lying in the same general plane, cord-securing means on the frame spaced at predetermined intervals according to some mathematical law or theory, a plurality of chalk-receiving cords temporarily secured at opposite ends to said cordsecuring means and stretched across the opening in the frame, the frame consisting of a plurality of separable sides, means to secure the separable sides together at their ends, said frame being four-sided, each of the sides having cord-securing means in a certain sequence or series, each pair of opposite sides having the same series, the series of one pair of opposite sides differing from the series of the other pair, so that many different sets of parallel and crossing chalk lines may be marked on a blackboard.

2. A device of the character described comprising a rigid rectangular frame having a central opening and lying in the same general plane, cord-securing means on the frame spaced at predetermined intervals according to some math ematical law or theory, a plurality of chalk-receiving cords temporarily secured at opposite ends to said cord-securing means and stretched across the opening in the frame, the frame consisting of four rigid frame members and four corner pieces, each corner piece being insertible partly in the ends of two frame members at right angles to each other, and means to secure each corner piece to the adjacent ends of two of the rigid frame members, the parts being constructed and arranged so that the two outer faces of each corner piece are flush with the respective outer faces of the two frame members which are joined together by the corner piece.

3. A device of the character described, comprising a rigid open frame consisting of a plurality of separable parts and means for securing the separable parts together, the frame being flat so that it may lie flat against a blackboard or other lane surface, said frame having cordsecuring means arranged on opposite sides at predetermined intervals according to some mathematical law or theory, and a plurality of chalking cords stretched across the frame opening under tension and temporarily secured by said securing means according to a predetermined plan so as to lie in substantially the same plane; the frame being rectangular and being composed of four channels with four rigid angular corner pieces each of which fits snugly in the ends of two channel members at right angles to each other, the corner pieces being held in the channels wholly by friction.

4. A device of the character described comprising a rigid open frame consisting of four channel members and four corner pieces removably secured to the ends of the channel members at the four corners of the frame, each of the channel members having cord-receiving means spaced along the top edges of both of the flanges of the channel, the spacing of the cordreceiving means being according to some mathematical law or theory, a plurality of cords adapted to be placed in said cord-receiving means and stretched across the opening in the frame, stop means on the ends of the cords and engaging the flange having the cord-receiving means to hold the cords in tension, the bottoms of at least two 6 of the channels having apertures through which the ends of the cords and the stop means thereon may be passed, said apertures being aligned transversely of the channels with the cord-receiving means on one of the flanges thereof.

5. The invention defined in claim 4, wherein the cord-receiving means are notches extendin downwardly from the tops of the flanges, and the apertures are triangular with the apexes of the triangles aligned with the centers of the notches on one of the flanges.

6. Means for securing ends of cords having stop means to a frame having channel members, said means consisting of apertures in the bottom or webs of the channel members and notches formed in the top edges of the flanges of the channels, the parts being so constructed and arranged that there is one aperture for each notch in one of the flanges and the centers of the apertures lie in the same transverse planes as the centers of the corresponding notches, and furthermore the end of each cord may be held by its stop means after the cord is wrapped around the outside of the channel and engaged with a notch on the outside flange or alternatively after the cord and its stop means are passed through an aperture and up inside the channel and the cord is passed through the notch which lies in the same plane as said aperture, with the stop means back of the last mentioned notch.

'7. The invention as defined in claim 6, wherein the apertures are each triangular with their apexes directed toward the notches in their transverse planes, the converging walls of the apertures serving to align a cord relative to a notch and also acting to frictionally grip the cord in assembling.

8. A device of the character described comprising a rigid frame having a central opening and lying in the same general plane, cord-securing means on opposite sides of the frame spaced apart in accordance with a single logarithmic series, a plurality of chalk-receiving cords temporarily secured at opposite ends to said cordsecuring means and stretched across the opening in the frame, the frame consisting of a plurality of separable sides and means to secure the sep-- arable sides together at their ends.

9. A device of the character described comprising a rigid frame having a central opening and lying in the same general plane, cord-securing means on opposite sides of the frame spaced apart in accordance with a double logarithmic series, a plurality of chalk-receiving cords temporarily secured at opposite ends to said cordsecuring means and stretched across the opening in the frame, the frame consisting of a plurality of separable sides and means to secure the separable sides together at their ends.

10. A device of the character described comprising a rigid frame having a central opening and lying in the same general plane, cord-securing means on opposite sides of the frame spaced apart in accordanc with the mathematical theory of probability, a plurality of chalk-receiving cords temporarily secured at opposite ends to said cord-securing means and stretched across the opening in the frame, the frame consisting of a plurality of separable sides and means to secure the separable sides together at their ends.

11. A device of the character described comprising a rigid rectangular frame having a central opening and lying in the same general plane, cord-securing means spaced in a double logarithmic series along to corresponding edges of the frame on opposite sides and other cord-securing nd n he amewmqppesite a pl alxtsi or. walkeam ng, cexdsitex poraril se ui at pp site nds/r1 9; aid co dr sw r means an tre che mssh h op nin in he mm the me n is ing o apl'ixmli ienarable. Sides. nd eans. 05 29 11 hep ble. s d stogether at. heir ends,

12. A deyieefioj the character described comprising a, rigid rectang gla r fgame haying acen: r l g ningg ndilx n n he am en ralp n a de urin msans p sed n a d le osa i hr mi rie elem; mmcq li smn in edges ,5 th frame on t w.o oppositefisides, other cord-securing meansspagegl in] aes ingle logarithmic series alon the other twp cgrresgdn ding edges of the frame. on the same two ppositesides, other, cord-securmg m nssnaq d ev nly al n tw o r o in edges oi the; fzgame on, the other two opposite sides, and. still ether cqyflr-sfimlling means esp-aged mm acc rd ng, a hema s l or f plfobability along the la st smentioneq opposite ide talnns es dif erin r m hes mvided with the evenly. spa gegi securing means, a

PAUL E: WHITTINGTON:

Refepegces Qjjqed int he fileojthis patept.

UNITED STATES PATENTS Number 1 1,3 PM? 253,499 Allen Feb. 14, 1832 683,115 Gilliam Sept. 24, 1901 ,072 Buda Sept; 1,622,229 Ormiston Mar. 22,192! 1,898,297 Fox Feb, 21, 1933 1,997,539 Beehhoier Apr. 9,1935 2,218,175 M2101; Oct 15, 1940 2,292,356 Belanger Aug. 11, 1942 FOREIGN BATENTS. Number- Country Date 4 ,558v Great Britain Mar. 26, 1887;

14,934. Great Britain Oct. 6, 1900 

